Abstract
The alkaliphilic halotolerant bacterium Bacillus sp. N16-5 is often exposed to salt stress in its natural habitats. In this study, we used one-colour microarrays to investigate adaptive responses of Bacillus sp. N16-5 transcriptome to long-term growth at different salinity levels (0%, 2%, 8%, and 15% NaCl) and to a sudden salt increase from 0% to 8% NaCl. The common strategies used by bacteria to survive and grow at high salt conditions, such as K+ uptake, Na+ efflux, and the accumulation of organic compatible solutes (glycine betaine and ectoine), were observed in Bacillus sp. N16-5. The genes of SigB regulon involved in general stress responses and chaperone-encoding genes were also induced by high salt concentration. Moreover, the genes regulating swarming ability and the composition of the cytoplasmic membrane and cell wall were also differentially expressed. The genes involved in iron uptake were down-regulated, whereas the iron homeostasis regulator Fur was up-regulated, suggesting that Fur may play a role in the salt adaption of Bacillus sp. N16-5. In summary, we present a comprehensive gene expression profiling of alkaliphilic Bacillus sp. N16-5 cells exposed to high salt stress, which would help elucidate the mechanisms underlying alkaliphilic Bacillus spp. survival in and adaptation to salt stress.
Highlights
In their natural habitats, bacteria are often confronted with physicochemical changes in the environment, including osmolarity, pH, temperature, and oxygen concentration [1]; the ability to adapt to changing and often harsh environments is critical for bacterial survival
N16-5 growth at different salinities showed that the optimal salinity was 2% NaCl (Fig 1)
We performed comprehensive transcriptomics analysis of the mechanisms underlying the adaptation of alkaliphilic Bacillus sp
Summary
Bacteria are often confronted with physicochemical changes in the environment, including osmolarity, pH, temperature, and oxygen concentration [1]; the ability to adapt to changing and often harsh environments is critical for bacterial survival. The tolerance to salinity and osmotic stress has been studied in a number of bacterial species such as Escherichia coli and Bacillus subtilis [2,3]. The common strategy used by bacteria to adapt to high salt concentrations is based on the biosynthesis and/or accumulation of organic compatible solutes that do not interfere greatly with the activity of normal enzymes and function as osmoprotectants against high salinity [4,5]. Organic compatible solutes used by various microorganisms include, among others, glycine betaine, proline, trehalose, and ectoine [6,7,8].
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